Specifications

Operation Manual
Studio Reference I & II Professional Studio Amplifiers
page 22
FAULT
ONLY ONE CHANNEL SHOWN
NPN HI
OUTPUT
STAGE
NPN LOW
OUTPUT
STAGE
PNP LOW
OUTPUT
STAGE
PNP HI
OUTPUT
STAGE
+
OUTPUT
+Vcc
–Vcc
TRANSLATOR
LVA
LVA
+Vcc
–Vcc
BIAS
CURRENT
LIMIT
TRANSLATOR
BALANCE
INPUT STAGE
P.I.P.
BALANCED
INPUTS
1/4" PHONE
XLR
VARIABLE
GAIN STAGE
ERROR
AMP
DISPLAY
BIAS
BRIDGE
BALANCE
+Vcc
–Vcc
POWER
SUPPLY
CONTROL
DC/LF
TIMER
POWER
+Vcc
–Vcc
ODEP
A
B
A
(ODEP)
B
(ODEP)
SUPPLY
D
E
(DISPLAY)
D
C
(DISPLAY)
E
HS
TEMP
C
(ODEP)
+24
–24
ENABLE
OVER
VOLTAGE
5 Principles of Operation
5.1 Overview
Studio Reference amplifiers incorporate several new tech-
nological advancements including real-time computer
simulation of output transistor stress, low-stress output
stages, an advanced heat sink embodiment and the Pro-
grammable Input Processor (PIP) expansion system.
Custom circuitry is incorporated to limit temperature and
current to safe levels making it highly reliable and tolerant
of faults. Unlike many lesser amplifiers, it can operate at
its voltage and current limits without self-
destructing.
Studio Reference amplifiers are protected against all com-
mon hazards that plague high-power amplifiers including
shorted, open or mismatched loads; overloaded power
supplies, excessive temperature, chain-destruction phe-
nomena, input overload and high-frequency blowups. The
unit protects loudspeakers from input and output DC, as
well as turn-on and turn-off transients.
Real-time computer simulation is used to create an ana-
logue of the junction temperature of the output transistors
(hereafter referred to as the output devices). Current is lim-
ited only when the device temperature becomes exces-
sive—and only by the minimum amount necessary. This
patented approach maximizes the available output power
and eliminates overheating—the major cause of device
failure.
Crown also invented the four-quadrant topology used in
the output stages of each Studio Reference amplifier (see
Figure 5.1). This special circuitry is called the grounded
bridge. It makes full use of the power supply by delivering
peak-to-peak voltages to the load that are twice the voltage
seen by the output devices.
As its name suggests, the grounded bridge topology is ref-
erenced to ground. Composite devices are constructed to
function as gigantic NPN and PNP devices to handle cur-
rents which exceed the limits of available devices. Each
output stage has two composite NPN and two composite
PNP devices.
The devices connected to the load are referred to as “high-
side NPN and PNP” and the devices connected to ground
are referred to as “low-side NPN and PNP.” Positive cur-
rent is delivered to the load by increasing conductance
simultaneously in the high-side NPN and low-side PNP
stage, while synchronously decreasing conductance of the
high-side PNP and low-side NPN.
The two channels may be used together to double the volt-
age (Bridge-Mono) or the current (Parallel-Mono) pre-
sented to the load. This feature gives you the flexibility to
maximize power available to the load.
A wide bandwidth, multiloop design is used for state-of-
the-art compensation. This produces ideal behavior and
results in ultra-low distortion values.
Aluminum extrusions are used widely for heat sinks in
power amplifiers due to their low cost and reasonable per-
formance. However, measured on a watts per pound or
watts per volume basis, the extrusion technology doesn’t
perform nearly as well as the heat sink technology devel-
oped for Studio Reference amplifiers.
Figure 5.1
Circuit Block Diagram